Engine Runs A Short Time Then Stalls

[daveson]

Make sure the FU computer (fuel injection control unit, under the seat) is plugged in fully home.

[daveson]

I had a problem similar to this. The bike would go for about one minute, then stop. After endless hours of research, thinking about it, motobrick, and working on it, the problem disappeared as quick as a flash, after replacing that bloody FU computer.

Note to self for the one hundredth time, do the quick easy stuff first.

[85killzillaRS]

¡¡¡ ok !!!
Ï started it, let it warm for a min & then drove 1/4 mi stopped and put a gallon of super. Then drove around neighborhood for about 15 min, 2nd & 3rd gear. Then it died, as if something was just turned off. It wouldn’t fire. The red light with triangle in middle of dash is on now. Ï did have bottle of ice water to cool the hall sensor. Ï pushed it home, maybe 1/4 mile. This was all maybe 2hrs ago. It’s in front, Ï went out a little while ago; same deal, gas is flowing but no spark. The one thing Ï did notice is that red light in dash is on when Ï turn key on. I’ll let it sit for a few hrs and try again?!
kind of makes me miss my ZX10

[Laitch]

The one thing Ï did notice is that red light in dash is on when Ï turn key on.

On a moto without ABS in the USA, the sole purpose of that light is to indicate the condition of the brake and tail light bulbs. To shut it off, you squeeze the front brake hand lever and push the rear brake pedal. If the brake light and tail light bulbs work, the light will turn off. If it doesn't turn off, then check those bulbs for function.

[85killzillaRS]

ok, Ï downloaded the pdf troubleshooting guide earlier. Ï did go for a cruise today close to home 2nd & 3rd gear mostly. it ran real well for about 15 min, then died. Like if something just turned off. i’ll go through the pdf & clean the fuel injection and ignition units as mentioned by Laitch THANK YOU

[The Mighty Gryphon]

Bad brake switches will make that light come on as well.  Am dealing with an intermittent front brake switch right now.

[85killzillaRS]

yesterday Ï did go for a quick cruise. Ï ended up pushing home. bike wouldn’t fire, even after sitting outside for a while. The red light Ï mentioned is easy enough to turn off. Ï haven’t ridden it in so long Ï forgot a quick brake application does away with that.
So this morning Ï tried to fire and it made a quick rumble, and now won’t start. That’s newish. Anyway, i’ll put it on lift today and clean the two units and go through through troubleshooting guide Ï downloaded yesterday. Ï wish myself good luck, Im gonna keep after this until something happens

[alabrew]

Go to the section of the Guide that tests the Air & Water sensors and MAF at the connector and see what the values are before a ride a and what they are when it shuts off.

Heat also brings to mind expansion and that some connection is opening when it gets hot, finding it is another matter. 

[85killzillaRS]

it was 109F today, makes it easy to not go work in garage. Ï got everything off and it’s on lift. I went and got some spray electrical contact cleaner. The plan is to open anything Ï see under the tank and clean it up then reassemble. Ï parked it in  moms garage 15 yrs when it stopped pumping water. Ï ended up moving and beat up a Ducati and ZX10 for quite a while. Ï ended up buying a low mile 1985-K motor and threw it in recently. Pretty quick and easy actually. It’s just been sitting there. Several bolts on tail unit pulled out the other day, Ï superglued em back in and they work as they should now. It would make sense connections might have corroded or become dirty in some way. It’s 10:30PM here now and it finally dropped to 99F. I’ll get up early and work on it in AM.
to answer a previous question, yes radiator is full and catch can 1/2
Hopefully I’ll have it all back together and riding down the street by noon, maybe before triple digit temps

[volador]

99°F-109°F doesn't sound so bad. Its a dry heat right?

don't know your past history of this 85 K100 other then the engine swap



1) Do you have the 'vacuum or pressure switch' found mounted on the back of the throttle bodies

If present unplug and tape connector somewhere to harness
Plug port on throttle bodies #1
No longer needed

http://www.motobrick.com/index.php?topic=8494.0

https://www.k100-forum.com/t15097-what-is-this

2) Is the fuel pressure regulator connected properly?

check hoses to the Fuel Pressure Regulator found mounted behind the throttle bodies
    1-vacuum hose from throttle bodies to the bottom FPR
    2-middle hose from petrol fuel injection fuel rail
    3-top hose to petrol tank return line



3) need to ensure the tank venting is working properly not obstructed, discharge hoses are connected or "Air Accumulator Cup" is present & hose connected to it routed down the backside of right footpeg plate

possibly have the emissions check valve on the tank vent port/hose which is no longer needed and the engine block may or may not have the tubing/stud port circled below

Picture below you may remove/omit the tubing and gray check valve and cap off the tubing nipple/stub on the front of the block under the radiator shroud.
Or leave rubber tubing and gray check valve in place and disconnect from tank vent and plug rubber tubing with a bolt or suitable hardware.
This was BMW evapoative emission compliance of the time but later removed.





Service Bulletin 2228  http://www.motobrick.com/index.php/topic,4984.0.html

During moto use its possible for petrol and fumes to be expelled from tank especially when full. Sloshing petrol can be sucked up into the tubing vent and expelled under tank pressure.
Exterior petrol tank bottom has 2 tubing nipple piped into the tank for petrol fume vent and the water/rain drain collected from around petrol gas cap.

K100 may or may not have the air accumulator cup 16132307467 installed to collect any expelled petrol or water from tank nipples with 1 rubber hose connected and routed down
to lower right footpeg plate.

Or instead 2 rubber hoses will be connected direct to the petrol tank tubing nipples if there is no air accumulator cup. Again hoses routed down to lower right footpeg plate.

The hole at 6:30 is the water drain. The notch in the petrol tank cap has to line up to that hole. The indicated tubing is the tank vent.



1985 K100 petrol tank bottom
forward tubing/stub is tank vent
rear tubing/stub- petrol cap rain drain



AIR ACCUMULATOR




AIR ACCUMULATOR LOCATION



 

[85killzillaRS]

Ï don’t know the installed motor history, other than it has ran quite well several times. The problem was/is spark. I’ve pulled plugs and they look a little dark, what I’d expect from a motor that runs and then dies from lack of spark. I’ve got it pretty stripped down and have been cleaning anything in sight. Ï have been getting fuel the whole time, so I’m really looking to clean what Ï can. The frustrating thing is that is has ran recently and Ï haven’t noticed anything that tells me “a is not connected to b“ or feel something slowly degrade. Like running out of fuel or dirty air cleaner etc. I’m no master mechanic, but I’ve turned quite a few wrenches in my time. 107F now at 6:15P. Time for some dinner then I’ll get back on it for a while.

[daveson]

Did this problem only start after you opened the EFI? (under the seat) if so did it look good, including the dielectric grease? Maybe a problem somewhere there.

If not, going to earlier posts, the fan coming on before shutdown, and after one mile, is a strong sign of a false temperature signal. I think I have read that the ECU (or EFI?)  shuts down the engine when it detects overheating, to prevent damage, not sure though, can't seem to get this from the wiring diagram (maybe later models)

[volador]

A rich fuel situation can be caused by the above vacuum switch or a faulty temp sensor

If your lacking spark your ICU may be faulty when reaching a higher operating temp. Did you open up the black box under the tank?

[85killzillaRS]

ok some really good points have been made. I’m not ready to replace any expensive units quite yet. The temp sensor and vacuum switch are good places to start tonight. Hopefully ECU, EFI are ok. Ï might start with temp sensor. Seems inexpensive and easy to change. I’m gonna search around for a bit and try to find old one from previous motor. It should at least get me past the 15 min Ï have been able to log in. If that’s the case I’ll definitely want to buy a new one. Maybe Ï can get another ride in. For now, almost everything is off, so clean, clean, clean. It’s really good to have so much input from people around the globe with slightly different bricks and different viewpoints. THANK YOU ALL
Ï’m not quite ready to mortar this brick down yet 

[volador]

Temp sensor on coolant 'T' into engine block test for resistance either sensor 'spade terminals' to sensor body measures ≅ 2.5KΩ @ 20°C

test pins 10 and 5 on the ECU connector plug under the seat for resistance measures ≅ 2.5KΩ @ 20°C
Flat blade screwdriver, 'lever forward' in the hole of the tool-tray to loosen ECU connector plug

check the wires from Pin 10 & 5 of the fuel injection control unit plug for open or shorts

Pin 10 - violet/green
Pin 5- brown

more about LE-Jetronic diagnosis http://www.motobrick.com/index.php/topic,13440.0.html

[volador]

4) Petrol Tank Check Valve on the 1985 1-Hit Wonder

The petrol tank return check valve may be blocked/jammed with debris & rust. The ball and spring may be omitted to prevent restriction of flow.

Modification of the check valve assembly

http://www.kforum-tech.com/how-to/Modification%20for%20early%20gas%20tank.htm

[Laitch]

In Replies #2, #3 and #35, killzilla asserts the engine has no spark. He's arrived at his conclusion by looking at the spark plugs; however, judging from most of the replies being made in this thread, consensus seems to indicate he's out to lunch and should be looking at fuel supply.

I suggest he test each plug to verify its operation and help direct whether investigation should focus on fuel supply or spark to keep it from wandering all over the place.

[85killzillaRS]

very good point, I’m gonna keep cleaning
then I’ll be out to breakfast for bit before Ï close this up & try again

[85killzillaRS]

Ï saw a sig on here mentioning a sisyphean society,
that would be the nicest way to describe my project. It’s frustrating. Ï pulled all plugs. I’m getting fuel for sure. Last night Ï had it put back together, after removing & replacing tank Ï had it turning over and rumbling a bit. Ï stopped, pulled batt to recharge and went to bed. Today Ï got all ready to go and now it just turns over for a sec or two, then cuts out. Last night it would turn over for a while, just didn’t have enough fuel going through yet, after removing and replacing tank. Now it will turn a few sec, then stop. If Ï hold starter button, it’ll turn real quick, stop, then turn over again real quick, stop again, and just keep doing that. I’ve had several bikes before, all carbed and chain drive. So a few things are newish to me(ECU, EFI, shaft drive)
Ï thought for sure I’d be riding today. This intermittent starting thing is making me want to pull my hair out. Ï really do appreciate such varied input, maybe someone has experienced this before.   

[85killzillaRS]

KOKO
I’m just keeping on, keeping on
persistence

patience-Ï still have a little

[The Mighty Gryphon]

I just noticed that you have an early model K100.  Those bikes have a known problem with the ignition coils. 

Are your coils all black or do they have orange parts where the plug wires are connected? 

Have you pulled the spark plugs and checked them for spark when they are out of the engine?  If you did, were all the plugs not sparking or just some of them?  Which ones don't spark?

In your next post just answer my questions.  I have lived in El Paso and know how hot it gets in the summer so you don't have to bother me with weather reports.

Just answer the questions.

[The Mighty Gryphon]

This is what the good coils look like:


K100 coil.jpg (69.38 kB . 768x576 - viewed 494 times)

This is what the early coils with problems look like:


Funky coil.jpg (30.47 kB . 768x576 - viewed 487 times)

[85killzillaRS]

like daveson mentioned i’ve messed with all the quick and not so quick easy things,
as far as heat, it’s fried my hi/low switch and made some tails bolts pull. fixed that stuff.  so would heat affect coils like that, so they work, not work, then work again in morning. plus the temp firing like now. just pulled plugs, they all do fire. but they fire for a sec, stop then fire again for a sec; its not enough to get engine going. all plugs darkish, and Ï do have the orig black coils
haven’t lived here for a while and normally Ï rarely see over 100. been visiting, remodeling moms house, and trying to get the bumble beemer going. my summertime break before going back to school to be RN is slowly ending. I’d love to ride this thing back home to Santa Fe

[The Mighty Gryphon]

Dude, you gotta focus.  Answer my damn questions.

[85killzillaRS]

black coils
now only an intermittent spark

all plugs do spark
not frequent enough rythym to get it going